Gate valve



FIG. 1 is a front view of the gate valve embodying my design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a right side view thereof; and

FIG. 6 is a left side view thereof. 

The ornamental design for a gate valve, substantially as shown and described. 